1. Field of the Invention
The present invention relates to a chop saw for selectively cutting logs and other elongate, generally cylindrical workpieces to various lengths for further processing.
2. Description of the Prior Art
Known chop saws of the type described are large and heavy, having circular saw blades 6 feet or more in diameter capable of cross-cutting large logs of several feet or more in diameter. Chop saws of this size and type have commonly included a pivoted saw carriage oscillated by double-acting hydraulic cylinders to move the saw blade to and from the workpiece. However, in at least one case a rotating crank mechanism has been used to oscillate the saw carriage. Typically the speed of travel of the carriage during a cutting cycle is relatively constant whether oscillated by hydraulic cylinder or crank. Thus the carriage must be moved at a sufficiently slow speed to prevent overloading the saw motor as the saw cuts through a workpiece. However, because a considerable portion of the carriage travel occurs while the saw is not cutting, the overall cycling speed of constant-speed carriages is slow. Since the chop saw is usually positioned at the upstream end of a processing or production line of a mill or other processing plant, the cycling speed of the chop saw can determine or at least affect the production rate of a entire mill or plant. Thus it is advantageous to provide a chop saw with as fast a cycling speed as possible with the limits of the load capacity of the saw drive motor.
U.S. Pat. No. 3,715,946 discloses a chop saw of the general type previously described which endeavors to increase the overall cycling speed of the saw carriage by varying the feed speed in response to changes in the torque of the saw drive motor. A double-acting hydraulic cylinder is used to oscillate the saw carriage. The cycling speed control of such patent is complex, requiring feedback of torque signals from the electric saw motor to the hydraulic feed cylinder through sophisticated electrical, mechanical and hydraulic regulating components.
Other known saw devices have sought to vary the stroking speed of a saw by various usually complex means. Two such prior saws are shown in U.S. Pat. Nos. 2,987,085 and 3,213,734, neither of which, however, relate to chop saws of a type suitable for cross-cutting logs or other workpieces of large diameter.
Still another prior patent disclosing an unpowered saw carriage with means for feeding the saw through a workpiece at a variable speed is shown in U.S. Pat. No. 54,046.